Fuse



March 20, 1928. 1,663,333

J. H. CARMEAN FU'SE Filed. Nov. 2, 1925 INVENTOR hm [[(ammm ATTORNEYPatented Mar. 20, 1928.

UNITED STATES PATENT OFFICE.

FUSE.

Application filed November 2, 1925.

My invention relates to an electric fuse and more particularly to one ofthat type adapted to function by absorption of heat from externalsources, the principal object of the invention being to provide a fuseadapted for operation between two or more heating resistances, such asin an electric heater where two or more heat units are so employed as tooperate independently of each other, or together for providing thedegree of heat desired.

In accomplishing this and other objects of the invention I have providedimproved details of structure, the preferred forms of which areillustrated in the accompanying drawings wherein Fig. 1 is adiagrammatic view of two heating coils and their electric circuit,illustrating an adaptation of a fuse embodying my invention.

Fig. 2 is a detail perspective view of the fuse, showing its mounting indotted lines.

Fig. 3 is a detail perspective view of the fuse from the side oppositethat illustrated in Fig. 2.

Fig. 4 is a side elevational view of the fuse.

Referring more in detail to the drawings,

1 and 2 designate heat units comprising electric resistance coilsreceiving energy from an ordinary house lighting circuit comprising feedwires 3 and 4 connected by a switch 5 to the coil leads 6 and 7, thelead 6 being connected to a two point switch 8 adapted to connect thecoils into circuit through wires 9 and 10 leading from the lower ends ofthe coils. The lead 7 is connected as at 11 to a wire 12 joining theother ends of the coils so that the coils are connected in parallel andeither one or both of the coils may be energized, depending upon theposition of the switch 8. Thus, if the switch is moved so that its firstcontact is in position to connect the wire 9, the coil 1 is in operationand the coil 2 is out of the circuit, but if the switch is moved so asto connect both wires 9 and 10 to the lead 6, both coils are in circuitto generate heat.

To prevent damage to the heater from excessive heat, a fuse 13,constructed according to my invention, is interposed in the lead 7 andpreferably mounted between the coils 1 and 2 as illustrated in Fig. 1.The fuse comprises a metallic disk 14 carrying Serial No. 66,358.

hooked terminals 15 and 16 fixed to the disk at diametrically oppositepoints by a fusible solder as at 17 and 18. The terminals of the diskmay be connected to the wire 7 in any preferred manner, but I prefer toemploy spring arms 19 and 20, the ends of which are fixed to screws orterminals 21 and 22 in electrical connection with the lead 7, and thefree ends of the arms are spaced apart a greater distance than thelength of the fuse, so that when the hooked terminals are applied to thearms as shown in Fig. 2, the arms will be put under tension to causefirmer contact between the terminals and the arms, and when the fusiblematerial 17 and 18 is melted, the spring tension will help to pull thehooked terminals from the disk to break the circuit.

The fuse is so constructed that its fusing point is entirely undercontrol of the coil 1, so that when both coils are in operation the coil2 has no effect upon the fusing point of the fuse. This is accomplishedby providing the face of the disk adjacent the coil 1 with a blackenedand roughened surface 23, and the opposite face adjacent the coil 2 witha highly polished surface 24, so that it will readily absorb heat fromthe coil 1 but will reflect heat from the coil 2. This is an importantfeature, for if the fuse were so designed as to operate efficiently withthe first coil in operation and the reflecting surface not provided, thefuse would blow upon the second coil coming into circuit, due to thefuse absorbing additional heat from the second coil, and if the fusewere so designed as to receive this additional heat without fusing, itwould not blow when the first coil became overheated in operationindependently of the other coil.

The fuse constructed as described, operates as follows:

Supposing the coil 1 is the only coil in operation, the disk absorbsheat from the coil, but under normal conditions not enough to melt theconnections 17 and 18, but if an excessive amount of current flowsthrough the coil or if it be in operation for too long an interval, theexcessive heat will blow the fuse and interrupt fiow of current to thecoil, preventing damage to the heater.

If both coils are put into circuit, the additional heat from the secondcoil will not be absorbed by the fuse, but will be reflected mils, anda, link comprising a disk having opposite heat-reflecting andheat-absorbing 10 surfaces and hooks :fusibly attached to the disk andengaged with said resilient men1 hers, the hooks being tensioned by saidmembers towards separation from said disk.

In testimony whereof E affix my signature,

JAMES H. Ciilil /IEAN.

